Use a direct include of strings headers in ui/, part 2.

ui/base/models/menu_model.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_BASE_MODELS_MENU_MODEL_H_
 #define UI_BASE_MODELS_MENU_MODEL_H_
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 #include "ui/base/models/menu_model_delegate.h"
 #include "ui/base/models/menu_separator_types.h"
 #include "ui/base/ui_export.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/native_widget_types.h"
 
 
 namespace gfx {
 class Font;
 class Image;
@@ skipping 113 matching lines @@
   // true if an item with the specified command id is found. |model| is inout,
   // and specifies the model to start searching from.
   static bool GetModelAndIndexForCommandId(int command_id,
                                            MenuModel** model,
                                            int* index);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_MENU_MODEL_H_